• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.292-299
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• 2007

In gas turbine technology, the flame stability is inherently greater in conventional diffusion type combustion over a wider range fuel to oxidizer ratio. However, premixed type combustion which has narrow flame stability region, is widely used due to environmental reason. It has been observed in experiments that combustion instability of low frequency (${\sim}10Hz$) results from the modulation of equivalence ratio at fuel injection hole when a pressure fluctuation propagates upwards along the channel of the burner under an unchoked fuel flow condition. In this study, a commercial program was used to determine how the fuel flow rate changed with respect to the pressure, velocity of the fuel flow and the mass fraction in a choked and an unchoked condition. The calculation focuses on the upstream of the dump plane to know how the forced pressure with the fuel injection conditions affects the modulation of the equivalence ratio. Therefore, it is found that pressure fluctuation leads to oscillation of mass flow rate and then results in equivalence ratio modulation under the unchoked fuel flow condition.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.17-24
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• 2010

The objective of this work is to analyze the macroscopic behavior of spray and injection characteristics on the DME blended biodiesel at different mixing ratios by using spray visualization and injection rate measurement system. The spray images were analyzed to a spray tip penetration, a spray cone angle and a spray area distribution at various mixing ratio of DME by weight. The influence of different injection pressure and ambient pressure on the fuel spray characteristics are investigated for the various injection parameters. In order to analyze the injection characteristics of test fuels, the fuel injection rate is measured at various blending ratio. The variation of viscosity of the blended fuel by the mixing of DME fuel shows the improved effect of spray developments. Also, it was found that the injection quantities of high blended ratio were larger than that of lower blended fuel. Also, higher blending fuel showed a faster evaporation than that of mixing ratio of test fuel because kinetic viscosity was changed by blending ratio.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.356-363
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• 2005

The purpose of this paper is to investigate the optimal condition of the Syngas production by reforming of fuel using plasmatron. Plasma was generated by air and arc discharge. The effects of applied steam, $CO_2$ or Ni-catalyst on fuel conversion, as well as hydrogen yield and $H_2$/CO ratio were studied. When the variations of $O_2$/fuel ratio, $H_2O$/fuel flow ratio and $CO_2$/fuel flow ratio were $0.94{\sim}1.48$, $4.3{\sim}10$ and $0.8{\sim}3.05$, respectively. Under the condition mentioned above, result of $H_2O$/fuel flow ratio was maximum $H_2$ concentration, or $28.2{\sim}31.6%$, and result of $H_2O$/fuel flow ratio with catalyst was minimum CO concentration or $6.6{\sim}7.1%$. and $H_2$/CO ratio were $3.89{\sim}4.86$.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.5
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• pp.410-416
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~17% for 40 minutes, which rapidly decreased in the early stage of the performance evaluation but gradually decreased. The open circuit voltage ratio decreased with respect time; however, its time behavior was remarkably different with the reduction behavior of the peak power density ratio. The activation resistance ratio increased as ~15% for 40 minutes, which was almost similar with the time behavior of the peak power density ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.28-35
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• 2005

Fuel injection rate of an injector is affected by various injection conditions such as injection duration, fuel temperature, injection pressure, and voltage in LPG liquid injection systems for either a port-fuel-injection(PFI) or a direct injection(DI) in a cylinder. Even fuel injection conditions are changed, the air-fuel ratio should be accurately controlled to educe exhaust emissions. In this study, correction factor for the fuel injection rate of an injector is derived from the density ratio and the pressure difference ratio. A voltage correction factor is researched from injection test results on an LPG liquid injection engine. A compensation method of the fuel injection rate is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI-engine show that this system works well on experimental range of engine speed and load conditions. And the fuel injection rate is accurately controlled by the proposed compensation method.

• Plant Journal
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• v.12 no.3
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• pp.39-45
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• 2016

Each of fuel consumption per hour was measured at the 320 MW and 380 MW generator output while changing mixing ratio of bio fuel oil to 50%, 80% and 100%. Fuel consumption per hour was increased from 11.0% to 20.4% as mixing ratio of bio fuel oil was changed from 50% to 100% at the 320 MW generator output comparing with fuel consumption per hour in case of bunker-C oil single firing. Fuel consumption per hour was also increased from 12.0% to 21.1% as mixing ratio of bio fuel oil was changed from 50% to 100% at the generator output 380 MW. Furthermore, it was confirmed that plant efficiency was decreased as mixing ratio of bio fuel oil was increased from 50% to 100% as a result that plant efficiency was calculated using the measured fuel consumption per hour, the generator output and the gross heating value.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.37-43
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• 2010

The purpose of this paper is to investigate the effect of air-fuel ratio on the combustion and emissions characteristics of spark ignition (SI) gasoline engine fueled with bio-ethanol. A 1.6L SI engine with 4 cylinders was tested on EC dynamometer. In addition, lambda sensor and lambda meter were connected with universal ECU to control the lambda value which is varied from 0.7 to 1.3. The engine performance and combustion characteristics of bio-ethanol fuel were compared to those obtained by pure gasoline. Furthermore, the exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), oxides of nitrogen ($NO_X$) and carbon dioxide ($CO_2$) were measured by emission analyzers. The results showed that the brake torque and cylinder pressure of bio-ethanol fuel were slightly higher than those of gasoline fuel. Brake specific fuel consumption (BSFC) of bio-ethanol was increased while brake specific energy consumption (BSEC) was decreased. The exhaust emissions of bio-ethanol fuel were lower than those of gasoline fuel under overall experimental conditions. However, the specific emission characteristics of the engine with bio-ethanol fuel were influenced by air-fuel ratio.

• International Journal of Automotive Technology
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• v.7 no.3
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• pp.277-282
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• 2006

With the aim of achieving half the regulated value of EURO-3 Emission Regulations, an ultra low emission motorcycle has been developed based on a motorcycle with an 1800 $cm^3$, horizontal opposed 6-cylinder engine. For the fuel supply system, an electronically controlled fuel injection system was applied. For the emission purification system, three-way catalysts, a feedback control system with a LAF(Linear Air-Fuel ratio) sensor, and a secondary air induction system were applied. To reduce CO and HC emissions during cold starting, an early catalyst activation method combining RACV(Rotary Air Control Valve) and retarded ignition timing was applied. After the catalyst activation, air-fuel ratio was controlled to maximize the purification ratio of the catalyst according to vehicle speed. For the air-fuel ratio control system, the LAF sensor was used. Furthermore, fine adjustment by the LAF feedback control reduced torque fluctuation due to the air-fuel ratio change. As a result, smooth ride feeling was maintained. Owing to these technologies, half the regulated value of EURO-3 has been achieved without any negative impact to the large-scaled motorcycles' drivability. This paper presents the developed ultra low emission technologies including the control method using an LAF sensor.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.66-72
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• 1999

It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.219-226
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• 2002

Filtration performance of an automotive fuel filter was evaluated based on the theory of Beta ratio. This study also introduced the fuel components' contamination performance test stand incorporating the multi-pass filtration test circuit. The theoretical basis of multi-pass test and test procedure were described in detail. The specification of commercial fuel filter currently available was just the maximum pressure drop across the filter assembly and the holding capacity of contaminants. However, test results revealed that the fuel filter tested could not maintain consistent Beta ratio, that is filtration efficiency, although it had the holding capacity close to the specification. Hence the Beta ratio should be specified in service life. The results also showed that filtration system model should be refined including desorption ratio to estimate the variable Beta ratio in the test.